1. Field of the Invention
The present invention pertains to a drive apparatus for an opening and closing mechanism which is used in a ventilating system, a remote operated valve or the like.
2. Related Art
Conventional ventilating systems include shutters which are open during the operation of the systems. When the systems are not in operation, such shutters are closed to prevent wind and rain blowing into a room and to protect their fans, motors and the like of the systems.
To open and close such shutters, the following three methods have conventionally been practiced. First, the shutter as well as the fan motor may be operated interlockingly by manipulating a single pulling string. Secondly, the shutter may be opened by making use of wind pressure produced by, the fan and closed by its own weight when the fan stops. Thirdly, the shutter may be connected with the fan motor through a clutch mechanism or the like.
Among the above, the first method has drawbacks that a great force is required to manipulate the string, thus often causing difficulties to arise when operated by children or women. Besides, the place where the ventilation system may be located is comparatively limited due to the necessity of manipulating the string. In the second method, the force to be exerted on the shutter to open it is relatively small, and hence the shutter would not operate properly if a grease stain or the like has stuck to the system. Moreover, a strong outdoors wind may prevent the shutter from opening sufficiently, thus decreasing its ventilation capacity. In addition, such method cannot be applied to a ventilating system for introducing fresh air and expelling foul air.
Further, the third method requires a clutch which is responsive to the starting and stopping of the fan motor to transmit the rotational force of the fan motor to an opening and closing mechanism for the shutter. As such a clutch, a centrifugal clutch which makes use of centrifugal force of the rotation of the fan motor might be possibly employed. The clutch is, however intricate in construction, and susceptible to mechanical difficulties since the ventilating system may be easily soiled with grease, or the like. Furthermore, this method also cannot be used in a ventilating system employed both to introduce fresh air and expel foul air.